Quantum well model and variation of the optical band gap in hydrogenated amorphous silicon carbon alloy films

Abstract

In addition to the increase in the optical band gap ( E opt) with hydrogenation, interesting variation of E opt results with the increase in the carbon content ( x) and also annealing temperature ( T a) in the hydrogenated amorphous silicon carbon alloy films (a-Si 1− x C x :H). E opt increases with x, reaches a maximum and then decreases with the further increase in x while E opt initially decreases with T a and then increases with the further increase in T a. The present study demonstrates that the models based on alloying or/and ordering fail to explain both the variation of E opt with x as well as T a, and the proposed model, which is an extension of the Brodsky quantum well model (Solid State Commun. 36 (1980) 55) to hydrogenated amorphous silicon carbon alloys. However, it is the only model capable of explaining the experimental results, a fact which may have considerable implications.